I. Field of the Invention
This invention relates generally to spine surgery and, in particular, to methods and apparatus for treating spinal stenosis.
II. Discussion of the Prior Art
Spinal stenosis is a narrowing of spaces in the spine which results in pressure on the spinal cord and/or nerve roots. This disorder usually involves the narrowing of one or more of the following: (1) the canal in the center of the vertebral column through which the spinal cord and nerve roots run, (2) the canals at the base or roots of nerves branching out from the spinal cord, or (3) the openings between vertebrae through which nerves leave the spine and go to other parts of the body. Pressure on the spinal cord and/or exiting nerve roots may give rise to pain or numbness in the legs and/or arms depending on the location within the spine (e.g. cervical, thoracic, lumbar regions). While spinal stenosis generally afflicts those of advanced age, younger patients may suffer as well.
A variety of treatments have been undertaken to alleviate or minimize the effects of spinal stenosis. One such technique is a laminectomy, which involves removing the lamina portion from the pathologic region. By removing the lamina, this procedure enlarges the spinal canal and thus relieves the pressure on the spinal chord and/or compressed nerves. While generally effective, some consider lamimectomy disadvantageous in that, as with any procedure involving bone removal, the resulting region of the spine may be further compromised from a mechanical standpoint. Moreover, elderly patients frequently have co-morbidities that increase the likelihood of complications, such as increased back pain, infection, and prolonged recovery.
Still other efforts at treating spinal stenosis involve placing spacer devices within the inter-spinous space to indirectly decompress the stenotic condition. These systems are characterized by being secured at the superior and inferior spinous processes. Having both ends of the spacer device coupled to the respective spinous processes disadvantageously limits both flexion and extension of the spine at that location, when it is believed that limiting extension is the key to relieving spinal stenosis. Moreover, the prior art inter-spinous spacers are typically constructed from materials (e.g. metal) with properties substantially different than that of the spinous processes themselves, which raises questions of whether the spinous processes will remodel around the spacer and thereby lose their ability to distract and thereby alleviate spinal stenosis.
The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.